Optical-fibers or bundles of optical-fibers, are commonly used to transport laser radiation from a laser source to a site at which it will be used. Uses may include, for example, medical uses, such as laser treatment of pigmented skin lesions, photodynamic therapy, laser depilation, and industrial uses such as drilling, marking or heat-treating material.
Typically laser radiation exits an optical-fiber or optical-fiber bundle as a diverging beam. This beam often is focussed by one or more optical elements connected with the fiber bundle to a spot of a size appropriate for a particular use. In many applications, it may be impractical, if not impossible, for a user to detect the focus of such optical elements and locate a point at which the radiation is to be delivered, i.e., aim the laser radiation by the light of the laser radiation itself.
Such applications would include applications wherein the laser radiation was being delivered at an intensity too great to be delivered in an uncontrolled or erratic manner, whether the radiation was being delivered in the form of short-pulses or quasi-continuously. Such applications would also include, of course, applications in which radiation being delivered were in the ultraviolet or infrared spectral regions and thus invisible to the human eye.
One simple means of focus location and aiming would be to provide a mechanical spacer or probe device attached to the optical elements which could make contact with a surface to which the laser radiation was to be delivered. Contact would occur when the optical elements were at a focal distance from the surface. Such a spacer or probe, suitably aligned with the optical elements and optical-fiber bundle, could also include an aperture which indicated where radiation would be delivered on the surface. Such a system has several disadvantages. By way of example, it would be undesirable for use with materials which would be easily marred or distorted by contact such as thin glass or plastic materials. A mechanical system, particularly an aperture may interfere with an operator's view of a surface to be treated. Further an aperture in the path of laser radiation may be subject to heating and possible damage by the laser radiation.
One optical means of focussing and aiming laser radiation from a fiber bundle is described in U.S. Pat. No. 5,394,492 to Hwang, which discloses a high power semiconductor (diode) infrared laser system. In this system, the output of an array of individual diode-lasers is collected by coupling the output of each into an input end of an optical-fiber associated therewith and collecting the output-ends of the fibers into a bundle. One or more refractive optical elements are provided for focussing a diverging beam delivered by the bundled output-ends of the fibers. A system for aiming and focussing the beam is taught, wherein at least one of the diode-lasers emits light in the visible spectrum, and the fiber associated with that diode-laser is bundled with the remaining fibers. This provides that some portion of the beam output from the bundled fibers is visible, allowing the beam to be aimed and focussed.
While the aiming and focussing system of the Hwang patent is doubtless effective in certain applications, it requires that a laser array be specially configured to provide an aiming and focussing beam. This can significantly increase the cost of manufacturing and assembling the array. Further, given a constant total number of diodes in an array, the greater the number of diodes emitting visible light for aiming purposes, the less will be available for delivering infrared power for the application. Further, diode lasers are available only in a limited range of colors, primarily red.
There is a need for an aiming and focussing system for optical-fiber-delivered radiation which can be independent of a laser device or array providing the laser radiation to be delivered. Preferably the system should be capable also of providing a variety of aiming targets differing, for example, in shape or color.